Normally, a phenolic resin can be obtained by reacting phenol with an aldehyde compound in the presence of an acid catalyst or a base catalyst. In the presence of an acid catalyst, it is possible to obtain a thermoplastic novolak-type phenolic resin (hereinafter it may be referred to as “novolak resin”) which has a main chain in which phenol lines up with methylene chains. On the other hand, in the presence of a base catalyst, it is possible to obtain a thermosetting resol-type phenolic resin (hereinafter it may be referred to as “resol resin”) which has a hydroxymethyl group at its end. The novolak resin has been widely used as a binder, such as that of friction materials, general molding materials, laminated materials, shell mold, whetstones, casting materials and foaming materials, because of being strong and having an insulation property.
Furthermore, the novolak resin has been also used for photoresists and semiconductor sealing materials, etc. in the electronic material field.
For example, as a positive type photoresist, it is known to use a composition containing a novolak resin, which is soluble in an alkaline development solution, and a quinone diazide group such as naphthoquinone diazide. Furthermore, 2.38 mass % aqueous solution of tetramethyl ammonium hydroxide (hereinafter it may be referred to as “TMAH”) which is an organoalkali is used in photolithography. Unless there is a proviso in the present description, “alkaline development solution” refers to this solution.
In photolithography, the above composition is alkali developable after exposure and shows a high resolving power. Therefore, the composition has been used for such as a manufacture of IC (Integrated Circuit), LSI (Large Scale Integration), etc., a manufacture of liquid crystal display (LCD), and a manufacture of photomask which is a printing original plate of a semiconductor. Furthermore, a novolak resin also having an excellent heat resisting property has been used for the plasma dry etching.
In LCD, picture element has been miniaturized and pixel width has been required to be at a several μm level with the progress of technology continuing from STN (Super-twisted Nematic) to TFT (Thin Film Transistor), so resist is required to have a sensitivity corresponding to instant level. Important properties of resist are having a good sensitivity as a resist, being excellent in resolution of a resist pattern after development patterning, adhesion with substrate, heat resisting property and circuit linewidth uniformity (CD uniformity), and having a high residual film rate.
Furthermore, it is also an important property that dissolution in the alkali development solution is fast, in other words, the rate of dissolution in the alkaline development solution (hereinafter it may be referred to as “Alkali Dissolution Rate”) is large.
Because of having heat resisting property in these properties, as a resist a composition containing a novolak resin, which is soluble in an alkaline development solution, and a quinone diazide group such as naphthoquinone diazide has attracted attention.
Although there is an illustration of resist to improve heat resisting property, which has been considered with a use of alkylphenol such as xylenol and trimethylphenol, the improvement of heat resisting property was small. Furthermore, in case of raising softening point to improve heat resisting property by raising molecular weight, the raising molecular weight has caused a defect that sensitivity of resist decreases.
A resin obtained by making phenol, m-cresol, or p-cresol react with formaldehyde or a monohydroxy aromatic aldehyde is disclosed in Patent Publication 1 and Patent Publication 2. The resin is regarded as a phenolic resin for photoresist having all of high heat resisting property, high resolution and high sensitivity.
On the other hand, a composition containing an epoxy resin and a hardening agent is used as a semiconductor sealing material. Also, acid anhydride, phenolic resin, etc. are used as the hardening agents. Although a hardened material of an epoxy resin composition using an acid anhydride as the hardening agent has transparency, this hardened material is poor in heat resisting property, so its transparency is easy to deteriorate under a high temperature environment. Furthermore, there are a problem that desired moisture resistant property and storage stability can't be obtained, and other problems. Although an epoxy resin using phenolic resin as the hardening agent has heat resisting property and moisture resistant property, this epoxy resin has problems like coloring by oxidation in preservation of transparency.
As an epoxy resin composition having light transmission and moisture resistant property, a light-transmissive epoxy resin composition using a cyclic terpene skeleton-containing diphenol as the hardening agent is disclosed in Patent Publication 3.
In this way, a hardening agent to make epoxy resin have heat resisting property, moisture resistant property, and transparency in a good balance instead of spoiling these properties is required.
In Non-Patent Publication 1, a method for producing an alkoxy benzene containing a hexafluoroisopropanol group is disclosed.